I dont think you can solo an oscillator on the P12 like you can on the PE. You'll have to just turn the volume down on the other OSC or a quicker way would be to go into all osc mode, turn all osc down, go out of that mode and turn up the osc you want to solo. If you are trying to discern which osc is which while you are listening to all, try changing the pitch on the the osc in question. This way , you will hear which part of the sound is changing pitch which allows your ears to focus on that particular osc. hope this helps